A number of studies have found that human biology may be linked with political orientation. This means that an individual's biology may predispose them to a particular political orientation and ideology or, conversely, that subscription to certain ideologies may predispose them to measurable biological and health outcomes.
One 2011 study, for instance, found that subjects with right-wing (or conservative in the United States) political views have larger amygdalae, areas of the brain associated with emotional responses such as fear, anxiety, and aggression. Based on such findings, some scholars argue that genetic factors account for at least some of the variation of political views. However, there is considerable disagreement among experts as to whether biological explanations for differences in political orientation are methodologically sound, and many studies which purport to demonstrate a connection have not been replicated.
From the perspective of evolutionary psychology, conflicts regarding redistribution of wealth may have been common in the ancestral environment and humans may have developed psychological mechanisms for judging their own chances of succeeding in such conflicts. Some researchers speculate that such mechanisms may affect political views.
Brain studies
A 2011 study by cognitive neuroscientist Ryota Kanai at University College London found structural brain differences between subjects of different political orientation in a convenience sample of students at the same college. The researchers performed MRI scans on the brains of 90 volunteer students who had indicated their political orientation on a five-point scale ranging from "very liberal" to "very conservative".Ninh, Amie (April 8, 2011). "Liberal vs. Conservative: Does the Difference Lie in the Brain?". Time.
Students who reported more conservative political views were found to have larger amygdala, a structure in the temporal lobes whose primary function is in the formation, consolidation and processing of memory, as well as positive and negative conditioning (emotional learning). The amygdala is responsible for important roles in social interaction, such as the recognition of emotional cues in facial expressions and the monitoring of personal space, with larger amygdalae correlating with larger and more complex social networks. It is also postulated to play a role in threat detection, including modulation of fear and aggression to perceived threats.T.L. Brink. (2008) Psychology: A Student Friendly Approach. "Unit 4: The Nervous System". pp 61. Conservative students were also found to have greater volume of gray matter in the left insula and the right entorhinal cortex. There is evidence that conservatives are more sensitive to disgust and one role of the insula is in the modulation of social emotions, such as the feeling of disgust to specific sights, smells and norm violations.
Students who reported more liberal political views were found to have a larger volume of grey matter in the anterior cingulate cortex, a structure of the brain associated with emotional awareness and the emotional processing of pain. The anterior cingulate cortex becomes active in situations of uncertainty, and is postulated to play a role in error detection, such as the monitoring and processing of conflicting stimuli or information.
The authors concluded, "Although our data do not determine whether these regions play a causal role in the formation of political attitudes, they converge with previous work to suggest a possible link between brain structure and psychological mechanisms that mediate political attitudes." In an interview with LiveScience, Ryota Kanai said, "It's very unlikely that actual political orientation is directly encoded in these brain regions", and that "more work is needed to determine how these brain structures mediate the formation of political attitude." Kanai and colleagues added that it is necessary to conduct a longitudinal study to determine whether the changes in brain structure that we observed lead to changes in political behavior or whether political attitudes and behavior instead result in changes of brain structure.
A 2024 study by Petalas et al achieved a partial replication of Kanai et al, using a larger sample size of 928 subjects, making it the largest preregistered replication study in political neuroscience to date. A positive relationship between the size of the amygdala and right-wing political views was found but at approximately a third of the effect size of the original study (r = 0.068 vs r = 0.23). The study also did not find a replication of the original finding of a positive relationship between a larger volume of grey matter in the anterior cingulate cortex and left-wing political views.Petalas, D. P., Schumacher, G., & Scholte, S. H. (2024). Is political ideology correlated with brain structure? A preregistered replication. iScience.
Intelligence A 2022 meta-analysis of cognitive studies found a "weak average association" between cognitive abilities and economic conservatism. It found support for two contrary effects in this relationship - the self-interest of economically higher status individuals supporting a relationship between economic conservatism and cognitive ability, and the need for certainty, which operated to diminish that relationship. However, it warned that the extant research it drew on was heterogenous in form, with different sampling methods, different locations, and different definitions producing different results.
Functional differences
Psychometrics
Various studies suggest measurable differences in the psychological traits of liberals and conservatives. Conservatives are more likely to self-report larger social networks, greater happiness and self-esteem than liberals, are more reactive to perceived threats and more likely to interpret ambiguous facial expressions as threatening. Liberals, in some studies, are more likely to report greater emotional distress, relationship dissatisfaction and experiential hardship than conservatives, and show more openness to experience as well as greater tolerance for uncertainty and disorder. However, the relationship between openness to experience and political orientation is correlational rather than causal. One 2025 research paper found that, regarding the previously reported mental health gap between ideological groups, "asking instead about overall mood eliminated the gap between liberals and conservatives." That paper suggested that concepts of "mental health" had "become increasingly politicized in the US", and "rather than a genuine mental health divide, conservatives may inflate their mental health ratings when asked, due to stigma surrounding the term. Another possibility is that ideological differences persist for some aspects of mental well-being, but not others."
Behavioral studies
A study by David Amodio et al. at New York University and the University of California, Los Angeles, found differences in how self-described liberal and conservative research participants responded to changes in patterns.David M Amodio, John T Jost, Sarah L Master & Cindy M Yee, Neurocognitive correlates of liberalism and conservatism, Nature Neuroscience. Cited by 69 other studies Participants were asked to tap a keyboard when the letter "M" appeared on a computer monitor and to refrain from tapping when they saw a "W". The letter "M" appeared four times more frequently than "W", conditioning participants to press the keyboard when a letter appears. Liberal participants made fewer mistakes than conservatives during testing and their electroencephalograph readings showed more activity in the anterior cingulate cortex, the part of the brain that deals with conflicting information, during the experiment, suggesting that they were better able to detect conflicts in established patterns. Amodio warned against concluding that a particular political orientation is superior. He said: "The tendency of conservatives to block distracting information could be a good thing depending on the situation."
A 2017 study both replicated the original study and also found that conservatives performed better in a task in which choosing the simple strategy was the more optimal solution; while both liberals and conservatives started the task attempting the more complex but less effective strategy, conservatives switched to the simple strategy more quickly than liberals.Bernabel, R. T., & Oliveira, A. (2017). Conservatism and liberalism predict performance in two nonideological cognitive tasks. Politics and the Life Sciences, 36(2), 49-59. Amodio's original study was also replicated by Weissflog et al. (2013)Weissflog, M., Choma, B. L., Dywan, J., van Noordt, S. J., & Segalowitz, S. J. (2013). The political (and physiological) divide: Political orientation, performance monitoring, and the anterior cingulate response. Social neuroscience, 8(5), 434-447. and Inzlicht et al. (2009).Inzlicht, Michael, Ian McGregor, Jacob B. Hirsh, and Kyle Nash. "Neural markers of religious conviction." Psychological science 20, no. 3 (2009): 385-392. Conversely, Kremláček et al. (2019)Kremláček, Jan, Daniel Musil, Jana Langrová, and Martin Palecek. "Neural correlates of liberalism and conservatism in a post-Communist country." Frontiers in Human Neuroscience 13 (2019): 119. and Wendell (2016)Wendell, D. G. (2016). Loyola eCommons Neural Correlates of Political Attitudes: Emotion and Ideology in the Brain. Available online at: http://ecommons.luc.edu/luc_diss/2299, Loyola University Chicago, pages 133-178 Accessed 27/07/2023 did not replicate Amodio's results. Both studies also argued that Weissflog and Inzlicht's results were not as concordant with the Amodio's findings as originally claimed.
A study of subjects' reported level of disgust linked to various scenarios showed that people who scored highly on the "disgust sensitivity" scale held more politically conservative views, which some researchers believe could be partially explained by personality traits.Xu, Xiaowen, Annika K. Karinen, Hanah A. Chapman, Jordan B. Peterson, and Jason E. Plaks. "An orderly personality partially explains the link between trait disgust and political conservatism." Cognition and Emotion (2019). However, the findings of a 2019 study suggest that sensitivity to disgust among conservatives varies according to the elicitors used, and that using an elicitor-unspecific scale caused the differences in sensitivity to disappear between those of different political orientations.Elad-Strenger, Julia, Jutta Proch, and Thomas Kessler. "Is Disgust a "Conservative" Emotion?." Personality and Social Psychology Bulletin (2019): 0146167219880191.
A 2018 study of 15,001 participants in the United States looking at levels of cognitive reflection (the tendency to favour analytic reasoning over instinctive or "gut" responses) found that those who voted for Donald Trump in the 2016 US presidential election had lower levels of cognitive reflection than Hillary Clinton voters or third-party voters. However, this effect was mostly driven by Democrats who voted for Trump, while amongst Republicans, Clinton and Trump voters had more similar levels of cognitive reflection. Republicans who voted for third-party candidates or those who identified as libertarian had the highest levels of cognitive reflection.Pennycook, Gordon, and David G. Rand. "Cognitive reflection and the 2016 US Presidential election." Personality and Social Psychology Bulletin 45, no. 2 (2019): 224-239.
Physiology
Oxley et al. (2008) found that people with right-wing views had greater skin conductance response, indicating greater sympathetic nervous system response, to threatening images than those with left-wing views. However, subsequent studies with substantially greater statistical power failed to replicate these findings.